1. Field of the Invention
The present invention relates to a rotating gantry of a particle beam therapy system, and more particularly to a rotating gantry suitable for use in a particle beam therapy system for irradiating an ion beam, such as a proton or carbon ion beam, to an affected part of the patient body for treatment.
2. Description of the Related Art
There is known a therapy method of setting an isocenter (irradiation target center) to an affected part of the patient body, e.g., a cancer, and irradiating an ion beam, such as a proton or carbon ion beam, to the affected part. A particle beam therapy system for use with that therapy method comprises, for example, an ion beam generator, a beam line, and an irradiation device installed in a rotating gantry. The ion beam accelerated in the ion beam generator reaches the irradiation device through the beam line and is irradiated to the affected part of the patient body from the irradiation device. At that time, the irradiation device is rotated around the patient body with rotation of the rotating gantry, thus enabling the ion beam to be irradiated to the affected part in accordance with the irradiation angle decided in a treatment plan.
Generally, the rotating gantry comprises a front ring, a rear ring, and a gantry barrel connecting the front ring and the rear ring by linear braces at plural points in the circumferential direction. The front ring and the rear ring are each supported by a plurality of rotatable rollers such that the rotating gantry is rotatable in the circumferential direction of the front ring and the rear ring. Reinforcing members of a truss structure are provided around the gantry barrel to which the irradiation device is mounted, to thereby provide a structure for increasing the strength of the gantry barrel. Further, the plurality of rollers are arranged along outer peripheral (circumferential) surfaces of the front ring and the rear ring by using link frames each made up of a parent link member rotatably attached to a bracket which is fixed to a pedestal, and two child link members rotatably coupled to the parent link member (see, e.g., Patent Document 1; U.S. Pat. No. 4,917,344).